[U-Boot] [PATCH V3 1/3] lib_generic memcpy: copy one word at a time if possible

Chris Moore
2009-10-12T04:37:12Z

Hi Alessandro,

Alessandro Rubini a ?crit :
>>> + unsigned long *dl = (unsigned long *)dest, *sl = (unsigned long *)src;
>>>
>
>
>> Nitpick: Are you sure the casts are necessary here ?
>>
>
> Without the one on src it complains because of "const". So I write
> both for symetry.
>

Yes, of course, you and the compiler are absolutely right.
Silly me, I completely overlooked the const :(
To me casting away const is a cardinal sin (it rather defeats the
object) and I find that the ease with which it can be done in C is
frightening.
So I feel obliged to (hopefully) correct my submission:

void *memcpy(void *dest, const void *src, size_t count)
{
char *d8;
const char *s8;
unsigned long *dl = dest;
const unsigned long *sl = src;

/* while all data is aligned (common case), copy multiple bytes at a time */
if ( (((int)(long)dest | (int)(long)src) & (sizeof(*dl) - 1)) == 0) {
while (count >= sizeof(*dl)) {
*dl++ = *sl++;
count -= sizeof(*dl);
}
}

d8 = (char *)dl;
s8 = (const char *)sl;

/* copy any remaining data byte by byte */
while (count--)
*d8++ = *s8++;

return dest;
}

But this is still not even compile tested :(
I never learn :(

Cheers,
Chris